Automatic fire-alarm



(No Model.)

A. WATSON.

AUTOMATIC FIRE ALARM.

N0. 395,096. Patented Dec. Z5, 1888.

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UNITED STATES PATENT @rriicit.

ALEXANDER W.-\TSON, OF SAN FRANCISCO, CALIFORNIA.

AUTOMATIC FiRE ALARh-Jl.

SPECIFICATION forming part of Letters Patent No. 395,096, dated December 25, 1888.

Application tiled August 25, 1888. Serial No. 283,767. (No model.)

To all whom it may concern:

Be it known that I, ALEXANDER WArsoN, a subject of the Queen of Great Britain, residing in the city and county of San Francisco, and State of California, have invented certain new and useful Improvements in Automatic Fire-Alarms, of which the following is a specification.

My invention relates to devices that are actuated or set in motion by an excessive variation in the temperature of an apartment to make or break an electric circuit and sound an alarm; and it consists in certain novel construction and combination of parts, and the production of a device to give warning of an abnormal variation in the temperature to which the device is exposed, substantially as hereinafter described, and pointed out in the claim.

Devices of this kind are most generally employed as fire-alar1ns to give notice of an excessive increase in the temperature of an apartment, such as would be produced by he combustion of an inflammable substance in the vicinity of the device; but, while relating generally to the production of a fire-alarm for this purpose, it should. be mentioned that my invention is applicable, also, to other uses and purposes-such, for instance, as to give notice of the reduction as well as the increase in the temperature to which it is exposed.

Two different forms of my improved device are therefore illustrated in the accompanying drawings, that form a part of this specification.

Fignrel ol' the drawings represents a device suitable for a tire-alarm, and Fig. 2 shows another form suitable for many purposes where a variation in temperature, either above or below a given point. is to be indicated and an alarm given. Fig. is a plan of Fig. 1.

The same letters of reference are used to denote correspondin parts in the several figures of the drawings.

A represents a suitable basc, having a post or upright support, ll, on which is set a balanced beam, C, carrying a glass tube,l), with a bulb, 13 at one end. The beam is delicately balanced on knife-edge bearings, like a scale-beam, and the lass tube contains a body of quicksilver or spirit or other suitable fluid in a vacuum, like the ordinary thermometer-tube. By means of a conductor, X, the post 13 and beam C are electrically connected with one pole of a battery, TV, and by a second conductor, Y, a contact point or plate, E, on the base A, immediately under the beam, is electrically connected with the opposite pole of the same battery. The post and beam being made of some suitable conducting material, it will be seen that the electric circuit is established when the beam rests upon the terminal E of the conductor Y. The glass tube and the beam that carries it are then so adjusted that the movement of the quicksilver or fluid in the tube from the bulb toward the other end will destroy the equilibrium of the beam, and by throwing the greater weight *to the opposite side of the pivot will cause the beam to leave the point E and break the circuit. In this manner an electric bell, Z, in g the circuit will be sounded whenever the quicksilver or fluid in the tube is expanded by the increase of temperature to which the instrument is exposed.

The beam is provided with a sliding counter-balance, G, for regulating the delicacy of its movement, so that by setting this weight at ('litli'erent points on the beam the equilibrium will be dist-url; ed and the circuit broken l under different conditions or temperature, as

may be desired.

To make the instrun'icnt indical e a decrease instead of an increase in temperature it is only necessary to placc the contactpoiut E on the opposite side of thc pivot, as shown by the dotted lines in Fig. l, by which change the contraction of the quicksilver or fluid in the tube will produce prcpondcrancc of weight on the bulb side of the instrument, and thereby separate the beam and the contact-point.

In the construct ion rcprcsmited in Fig. 2 of the drawings the beam is balanced nicely over two contact-points, E and F, that are the terminals of two separate circuits. and the beam itself is electrically connected with the opposite pole of both circuits, so that as the beam is tipped either in one direction by the expansion of the quicksilver or in the other direction by its contraction, under the influence of the surrounding temperature, a circuit will be established and the bell sounded.

ICO

In this case it will be noticed that the instrument operates to complete instead of to break the circuit, and the electric bell connected with it will be arranged accordingly.

5 The scale S, Fig. 1,is provided for setting the weight G at the proper point along the ,beam to set off the instrument at any given degree of temperature. This scale is determined. at the time of manufacture by noting IO the degree of temperature at which the beam tips and makes or breaks the circuit when the weight G is placed at d itt'erent points, and then marking the degree in each case opposite the point on the scale over which the weight stands.

In situations where the instrument may be exposed to much yibratio'nas from running machinery or heavy traffictending to disturb the balance, the contact-point E can be fixed on the under side of the beam to project at right angle from it and dip into a cup of mercury that is in proper electric connection. In most cases of use, also, it will be best to cover the instrument with a wire screen, as indicated in Fig. 2, which will admit the heat of the surrounding atmosphere to the bulb, but will prevent any possible disturbance from flies and insects.

\Vhen properly constructed and adjusted, this device will indicate within five degrees of temperature.

Having thus fully described my invention, what I claim, and desire to secure by Letters Patent, is-

The herein-described device, consisting of a base, as A, having a scale, as S, a standard,

B, mounted upon said base, a balanced beam, 

